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From: "already5chosen at yahoo dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/97832] AoSoA complex caxpy-like loops: AVX2+FMA -Ofast 7 times slower than -O3
Date: Mon, 16 Nov 2020 20:11:37 +0000 [thread overview]
Message-ID: <bug-97832-4-jNhR40UY1K@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-97832-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97832
--- Comment #3 from Michael_S <already5chosen at yahoo dot com> ---
(In reply to Richard Biener from comment #2)
> It's again reassociation making a mess out of the natural SLP opportunity
> (and thus SLP discovery fails miserably).
>
> One idea worth playing with would be to change reassociation to rank
> references
> from the same load group (as later vectorization would discover) the same.
>
> That said, further analysis and maybe a smaller testcase to look at is useful
> here. There is, after all, the opportunity to turn "bad" association at the
> source level to good for vectorization when -ffast-math is enabled as well.
It turned out, much simpler kernel suffers from the same problem.
void foo1x1(double* restrict y, const double* restrict x, int clen)
{
int xi = clen & 2;
double f_re = x[0+xi+0];
double f_im = x[4+xi+0];
int clen2 = (clen+xi) * 2;
#pragma GCC unroll 0
for (int c = 0; c < clen2; c += 8) {
// y[c] = y[c] - x[c]*conj(f);
#pragma GCC unroll 4
for (int k = 0; k < 4; ++k) {
double x_re = x[c+0+k];
double x_im = x[c+4+k];
double y_re = y[c+0+k];
double y_im = y[c+4+k];
y_re = y_re - x_re * f_re - x_im * f_im;;
y_im = y_im + x_re * f_im - x_im * f_re;
y[c+0+k] = y_re;
y[c+4+k] = y_im;
}
}
}
May be, it's possible to simplify further, but probably not by much.
next prev parent reply other threads:[~2020-11-16 20:11 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-14 20:44 [Bug target/97832] New: " already5chosen at yahoo dot com
2020-11-16 7:21 ` [Bug target/97832] " rguenth at gcc dot gnu.org
2020-11-16 11:11 ` rguenth at gcc dot gnu.org
2020-11-16 20:11 ` already5chosen at yahoo dot com [this message]
2020-11-17 9:21 ` [Bug tree-optimization/97832] " rguenth at gcc dot gnu.org
2020-11-17 10:18 ` rguenth at gcc dot gnu.org
2020-11-18 8:53 ` rguenth at gcc dot gnu.org
2020-11-18 9:15 ` rguenth at gcc dot gnu.org
2020-11-18 13:23 ` rguenth at gcc dot gnu.org
2020-11-18 13:39 ` rguenth at gcc dot gnu.org
2020-11-19 19:55 ` already5chosen at yahoo dot com
2020-11-20 7:10 ` rguenth at gcc dot gnu.org
2021-06-09 12:41 ` cvs-commit at gcc dot gnu.org
2021-06-09 12:54 ` rguenth at gcc dot gnu.org
2022-01-21 0:16 ` pinskia at gcc dot gnu.org
2022-11-24 23:22 ` already5chosen at yahoo dot com
2022-11-25 8:16 ` rguenth at gcc dot gnu.org
2022-11-25 13:19 ` already5chosen at yahoo dot com
2022-11-25 20:46 ` rguenth at gcc dot gnu.org
2022-11-25 21:27 ` amonakov at gcc dot gnu.org
2022-11-26 18:27 ` already5chosen at yahoo dot com
2022-11-26 18:36 ` already5chosen at yahoo dot com
2022-11-26 19:36 ` amonakov at gcc dot gnu.org
2022-11-26 22:00 ` already5chosen at yahoo dot com
2022-11-28 6:29 ` crazylht at gmail dot com
2022-11-28 6:42 ` crazylht at gmail dot com
2022-11-28 7:21 ` rguenther at suse dot de
2022-11-28 7:24 ` crazylht at gmail dot com
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